Add the support of Azure OpenAI image generation

[bmoussaud]

Need for a projet, I implemented the support of Azure OpenAI for image generation. It's mainly a reuse of the design delivered by model/spring-ai-openai

[tzolov]

Hi @bmoussaud ,
Thank you for your contribution!

Can you please address the following remaining steps:

• Please update the AOT hints if the new client needs them. This demo code can help write a aot compliance sample.
• Add Azure Image Auto-Configuration under azure/openai with dedicated properties. You can use the OpenAI autconfiguration as a reference.
• Add azure-openai-image documentaion under the api/images section and add the page to the nav.adoc under the api/images section.

[bmoussaud]

• implemented the support of ImageGeneration on Azure/OpenAI, including Metadata
• update documentation